In this R29 application, studies are proposed to focus on the possible interaction between HIV Rev protein and a recently identified cellular factor termed REBP. Specifically, the interaction of REBP with the leucine-rich effector domain of other lentiviral Rev proteins and cellular export proteins will be examined. The functional relevance of REBP with various retroviral Rev and export proteins will be studied. The critical sequence element in REBP that mediates Rev-REBP interaction will be identified. The subcellular localization of HIV Rev and REBP will be examined by confocal laser microscopy.